The present invention relates to the field of chairs, and, more particularly to chairs having seats and seat backs mounted on chair frames so as to provide controlled pivotal movement about a plurality of axes.
Over the years, many designs have been developed for chairs, and particularly office chairs, with the goal of providing for some movement of the chair in response to the movement of the person sitting in the chair. This objective has been accomplished to a limited extent through designs that provide for unitary movement of the chair back and chair seat, or by designs allowing the chair back to move without relationship to and independently of the chair seat. However, these designs have either incorporated a fixed relationship between the movement of the seat and seat back, or have been designed so that the seat and seat back can move freely, but without consideration of seat and seat back response to the occupant of the chair. A number of mechanisms have been developed to permit chair back movement about one or two axes of rotation, but these approaches have not provided optimum comfort to and control by the occupant of the chair.
The development of tiltable chair seat backs has also seen some use of resilient, rubber-like mounting pads for attaching a chair seat back or cushion to a chair frame although these approaches have been somewhat successful, they have not permitted or provided for controlled movement about at least two axes of rotation, and thus, have not provided a satisfactory level of comfort.
The present invention is directed to a simple, improved office or work space chair having a separate seat and seat back mounted on a frame, thus permitting pivotal movement of the seat, seat back, or both, in response to the movement and physical characteristics of the occupant of the chair. A further object of the present invention is to provide a chair that is ergonomically enhanced, whereby the user is the synchronous factor in determining the relative positions of the seat and seat back.
Accordingly, one aspect of the present invention is to provide a chair of the type having a separate seat and seat back, that includes a chair frame having a rear segment and a mounting mechanism connecting the seat back to the rear segment. The mounting mechanism connects the seat back to the segment of the frame in such a manner as to permit controlled pivotal movement of the seat back about at least two, and preferably three or more axes of rotation. The construction of the mounting mechanism is simple, requiring relatively few parts, without the need for post-installation adjustment or maintenance. In the preferred embodiment, a generally circular-shaped resilient pad, such as natural rubber, is positioned between two plates to form the mounting mechanism; however, any suitable elastomer providing the required degree of Shore hardness may be used. The resilient pad should have a Shore hardness of between 45 and 100, but desirably between 80 and 90 and preferably about 85 to provide for maximum responsiveness to and control by the user. The size and thickness of the resilient pad may also be varied to provide either a lesser or greater degree of controlled movement. Desiritbly, the plates are embedded in the resilient pad such that the outside surfaces of the plates are substantially coplanar with corresponding outside edges of the resilient pad. The resilient pad provides limited torsional resistance to relative rotation between the two plates. The selection of the size, shape, and hardness of the resilient pad in combination with the ergonomic placement of the mounting mechanism, cause the seat back to xe2x80x9cfollowxe2x80x9d the seat occupant thereby ensuring continuous, even support to the occupant""s back.
Openings and slots are formed in and through the mounting mechanism for attaching the mounting mechanism to the rear segment of the frame and to the seat back In a preferred embodiment, the mounting mechanism further includes a slot extending inwardly from a peripheral edge of the mount. This preferred embodiment may further include a travel stop positioned in the slot and attached to the frame or to the seat back. The travel stop has a smaller sized or diameter portion positioned in the slot and a larger sized or diameter portion positioned in a cavity in the seat back or frame. The larger sized portion of the travel stop) limits the travel of the adjacent plate as the seat back is tilted backward or forward, and thus limits the travel of the seat back.
Another aspect of the present invention is to provide the chair described above whereby the seat back may be installed in two different configurations, depending on the desires of the occupant, Specifically, the chair has an approximately shoulder high seat back; however, the seat back can be optionally installed such that the high back portion is turned downward so that the chair will have a lower mid-height seat back. Thus, the resiliently mounted seat back of the chair offers a wide range of comfortable motion for the chair occupant.
A further aspect of the present invention is to provide a chair that further includes at least one, and desirably two, mounting mechanisms connecting the seat to the substantially fixed seat support, permitting movement of the seat in forward and rearward directions and limited movement from side to side For simplicity and economy, the mounting mechanisms are the same as those used to connect the seat back to the rear segment of the chair frame; however, a higher or lower Shore hardness for the resilient pad may be selected, depending upon the specific application and desires of the user. Likewise, the size of the resilient pads may be varied, or a single larger resilient pad may be used. A single resilient pad could be circular or oval to more closely conform to the width of the chair As with the mounting mechanism connecting the frame to the seat back, the thickness of the mounting mechanism can be varied to provide a greater or lesser degree of controlled movement. This selection and placement of the mounting mechanisms causes the seat to respond to and move with the occupant, thereby evenly distributing pressure on the occupant""s hips, buttocks, and thighs.
The present invention, with independent mounting mechanisms connecting the respective seat and seat back portions of the chair to the frame of the chair, provides a construction having three variables: position of the seat back, position of the seat, and the user""s body. Accordingly, because the mounting mechanisms are ergonomically located with respect to the seat and seat back and respond to and move with the individual occupant, the occupant""s body (size, weight, height, and center of gravity) is the synchronous variable that determines the other two, thereby maximizing the occupant""s comfort by evenly supporting the occupant""s body.